The present invention relates to the protection of electronic devices such as printed circuit boards and cards from unauthorized intrusion. More particularly, the present invention relates to an improved intrusion detection structure for use with such devices.
It is a usual requirement for many computer applications to protect data from unwanted access by an unauthorized user. Many software protection systems are known in the art to allow only selected users to access said protected data, with the use of a password or other identification methods. Communication of data on a network is protected from undesired detection by means of encryption methods. Passwords, encryption keys and other sensitive data are usually stored in memory components in the computer systems and need to be protected even more carefully from unwanted inspection. Software control and protection methods may be not enough to stop an experienced person from bypassing these protections and tampering with the computer hardware, e.g. by direct interrogation of memory components such as integrated circuit memory.
A possible protection from the above physical attacks is to provide some kind of detecting means which detects an attempted intrusion within a protected sensitive area and reacts by giving an alarm or even by destroying any sensitive information to avoid the loss of secrecy.
U.S. Pat. No. 5,790,670 discloses an intrusion detection mechanism having a metallic cover for protecting an encryption circuitry and a memory in which the encryption key is stored. The metallic cover has a top and a bottom side which are secured together by a screw. The screw merely functions to cause a switch arm to depress a switch button when the mechanism is in the desired, assembly mode. When the security screw is rotated, a circuit is activated (by opening of the button), the attempt to open the cover is detected and a destruct circuit is enabled which causes the memory to be erased. A drawback of this method is that the electromechanical switch utilized is subject to hot and cold temperatures, dampness and other deteriorating environmental conditions which can adversely affect the switch""s level of performance, especially after prolonged exposure to such conditions. Furthermore, a failure of the circuit itself may be caused by oxidation of the circuitry at various portions thereof as a result of such prolonged exposure.
For the reasons above, an improved and relatively simple mechanism for detecting the attempt to open the protecting cover of a protective enclosure would be desirable. It is an object of the present invention to alleviate the above drawbacks of the prior art.
According to one aspect of the present invention, there is provided a tamper resistant enclosure for protecting an electronic device comprising a first cover on a first side of said electronic device, a second cover on the opposite side of said electronic device, a plurality of fixing elements passing through the first cover and the device and securing the first cover to the second cover while forming a circuit, and detecting means for detecting the removal of at least one of said fixing elements (e.g., screws).
According to another aspect of the invention, there is provided an electrical assembly which includes an electronic device including an electrical circuit having sensitive information as part thereof, a tamper resistant enclosure, the electronic device being positioned within the enclosure, the enclosure including a first cover for being positioned substantially on a first side of the electronic device, a second cover for being positioned substantially on the opposite side of the electronic device from the first side, a plurality of fixing components passing through the first cover for securing the first cover to the second cover, the fixing elements adapted for passing through the electronic device and forming a part of the electrical circuit of the electronic device when the first cover is secured to the second cover, and a detector for detecting the interruption of the electrical circuit caused by at least the partial removal of at least one of the fixing elements.